Quartz oscillator mechanical resonant frequency measuring CCT - contains bridge circuit in PLL feedback loop and potentiometer set to null

摘要

A circuit determines the mechanical resonant frequency of a mechanically damped quartz oscillator (9) in an oscillator and contains a bridge (1) with the quartz in series with a resistor (Ry) in one arm and a compensation capacitor (Ck) in series with a second resistor (Rk) in the other arm. The bridge circuit is connected in the feedback loop of a PLL control loop. The second resistor is a potentiometer set to null the bridge's phase and to maximise the difference voltage between the two arms. USE/ADVANTAGE - Accurately maintains electrical resonance equal to mechanical resonance of quartz, e.g. for timing generation.